It combines Fetch Modi, allowing the user to have multiple Modi active at once. So far it has been shown to combine a Queue and a Stack to create a Queuestack Modus, with both the first and last cards being simultaneously accessible, as well as an Array and a Queue and a Stack to create an Array of Queuestacks. It has 6 slots, potentially allowing for much more complex Modus combinations.
It is possible that the order in which the cards are inserted alters the resulting hybrid Modus. For example, were the Array cartridge inserted before the others, John may have ended up with a Queuestack of Arrays, or something to that effect. Also of note is the fact that combining the Queue and Stack Modi caused John's Captchalogue Cards themselves to change in coloration and usage, while adding the Array card to the previous two only altered the Cards' organization within his Deck, except for the first card in each queuestack, which turned blue. This may be due to the obvious compatibility of the Queue and Stack Modi, which implies that the Modus Control Deck acts on modi in predetermined ways and may create unexpected combinations when dealing with a Modus with which it is unfamiliar, though this is subject to question, considering the Array Fetch Modus actually came with the Modus Control Deck.